1. Field of the invention
The present invention relates to a controlled-access apparatus for the agricultural food industries.
2. Description of the prior art
Known equipment for agricultural food industries such as mixing or kneading machines having stationary or rotary vessels are often provided with a safety device for preventing access to the vessel during operation. This safety device is usually a mechanical device which closes the space between the rotary tool-holder and the edge of the vessel opening.
This safety device is often constituted either by a metal grid or by a solid screen which can be opaque or transparent. This mechanical safety device has proved effective up to the present time for protecting the user against accidental bodily injuries but is attended by a disadvantage, however, in the preparation of agricultural food products. In fact, some agricultural food products require constant supervision of the state of products being prepared or control of the degree of their evolution or else call for the addition of other products or ingredients during operation of equipment units and in predetermined stages of operation whereas the presence of this mechanical safety device hinders or prevents this supervision or introduction of products or ingredients.
Furthermore, this mechanical safety device which is designed in the form of a grid or element having a complicated structure is not readily conductive to easy maintenance of hygiene which is essential in the case of equipment employed in agricultural food industries.
In machine-tools such as presses, electronic protection systems already exist that delimit a field of protection about dangerous operating parts and actuate the shutting-down of these machines once the operator's hand or any object crosses the protection field. These known electronic systems are highly suitable for these presses or machine-tools, given that the operations carried out by them such as stamping, swaging, etc. of a metal sheet do not require any further human intervention during operation in order to achieve a desired result. However, in the case of preparing agricultural products, as recalled in the preceding paragraph, in an apparatus for the agricultural food industries such as a mixer or kneading machine such human intervention is required. On the other hand, these known electronic protection systems present the same drawbacks in the equipment for the agricultural food industries, as those indicated herein-above of a mechanical safety device, since these protection systems actuate the shut-down of this equipment once the instruments or the utensils used in a control of the degree of evolution of the products in preparation or the ingredients that must be added to these products in preparation, cross the field of protection developed by these systems.